The Excalibur rounds "had an average impact distance of less than two meters versus a threshold requirement of 10 meters," said Michelle Lohmeier, Raytheon's deputy program manger, land combat product line.

The new IMUs, built by Atlantic Inertial Systems, Plymouth, England, were added over the past several weeks after reliability failures with the previous Honeywell-built IMUs.

The U.S. Army, which has taken delivery of tens of thousands of XM982s, had suspended deliveries of Excalibur because of the problem.

"The XM982 [Excalibur] round is required to operate in an environment that exceeds 15,000 times the force of gravity," an Army spokesman said July 30 in a written statement. "There was an inherent lack of design robustness in the qualified IMU configuration, which resulted in a failure rate of approximately 5 percent. We have not been able to conclusively trace the exact cause to a design or process issue."

Army officials said none of the rounds used in combat have had problems.